SYDNEY: Two people were missing and the body of a third was recovered from raging floodwaters as severe storms pounded northeastern Australia on Sunday, forcing more than 1,000 to flee their homes.

Army aircraft were deployed to help the emergency effort in northern Queensland state where ex-tropical cyclone Oswald unleashed punishing rains and localised tornadoes and floodwaters threatened several major towns.

One woman was plucked to safety in Biloela, about 600 kilometres (400 miles) northwest of the state capital Brisbane, after spending eight hours clinging to a tree.

In Gympie, north of Brisbane, people had been forced to retreat to the roofs of their homes to await rescue, town mayor Ron Dyne said.

A 27-year-old man was missing after he attempted to cross a swollen creek near Gympie and state Premier Campbell Newman said there were serious concerns for another young woman.

"Emergency services are searching for a young woman who reportedly drove into waters near Pacific Haven this morning, and we have grave fears for her safety," Newman told reporters.

Separately, police said the body of an elderly man had been recovered from waters north of Bundaberg, where the engorged Burnett River broke its banks and was expected to engulf 300 homes.

Bundaberg was among dozens of towns devastated by floods in Queensland two years ago which claimed 35 lives, and Newman said residents there were bracing for the river to peak above 9.0 metres (30 feet), well in excess of the 7.92m seen in 2011.

Further north, in Gladstone, about 900 homes had been evacuated and several towns in the region were already isolated by the rising waters.

Across the state some 58,000 homes were without power and that number was growing by the hour according to Newman.

"We are right in the middle of this now, I can hear it bucketing down on the roof as we speak," he said.

Treasurer Wayne Swan said the "full assets of the defence forces are on standby if required", telling reporters conditions were "extremely serious for a significant number of communities in southeast Queensland".

The Insurance Council of Australia declared a statewide catastrophe, noting there had already been "severe inundation... in several towns and cities" and that major flood warnings had been issued.

"Unfortunately, this catastrophe declaration is the result of the first cyclone to come close to the coast this season, and the weather bureau has warned it's highly possible we will see more before the end of summer," said ICA chief Rob Whelan.

At least one international flight was diverted from Brisbane to Sydney due to the high winds and Qantas has cancelled a number of domestic services, with the Sunshine Coast regional airport shut down.

A staggering 1-1.5 metres of rain was estimated to have fallen since the Oswald storms began.

Cyclones and floods are common in Australia's northeast during the warmer summer months. A massive inundation of Queensland in 2011 killed 35 people and brought Brisbane to a standstill for several days, swamping some 30,000 homes.

Brisbane was expected to be spared the kind of flooding seen two years ago.